1. Field of the Invention
The present invention relates to a test data processing apparatus and a test data processing method for processing test data obtained by testing defects of a sheet-shaped product having at least an optical film that is a member of an optical displaying apparatus.
2. Description of the Background Art
Conventionally, in a maker for producing an optical film, a band-shaped sheet-shaped product having an optical film member is produced by collecting and winding it in a roll form or on a different production line for each step. As this “band-shaped sheet-shaped product”, there are, for example, a polarizing plate source, a retardation plate source, and a laminate film source of a polarizing plate and a retardation plate used in a liquid crystal display device.
An adhesive agent is used for bonding this sheet-shaped product with an optical displaying unit. This adhesive agent is formed in advance as an adhesive layer on the sheet-shaped product, and further a release film (which may also be referred to as a separator) is formed for protection of the adhesive layer.
A conventional example of the steps for producing a sheet-shaped product having a polarizing plate with a laminate structure of FIG. 4 will be described below. First, as preliminary steps, there are (A) a step of obtaining a polarizer, where the polarizer is obtained by drying a polyvinyl alcohol (PVA) film subjected to a dyeing/crosslinking and stretching process, (B) a step of producing a polarizing plate, where the polarizing plate is produced by bonding a triacetylcellulose (TAC) film via an adhesive agent on both surfaces of the polarizer and laminating a polarizer protective layer; here, in the drawings, an antiglare process is performed in advance on the TAC film to be laminated thereon, (C) a step of bonding a separator and a protective film, where the separator is bonded via a strong adhesive agent on one surface of the polarizing plate (lower side in the drawings) and the protective film is bonded via a weak adhesive agent on the other surface (upper side in the drawings). Here, the strong adhesive agent is applied in advance on the separator, and the weak adhesive agent is applied in advance on the protective film. The strong adhesive agent applied on the separator is transferred to the TAC after releasing the separator. The weak adhesive agent applied on the protective film remains as it is formed on the protective film after releasing the protective film, so that substantially the weak adhesive agent is not transferred to the TAC. Through the above-described preliminary steps, a band-shaped sheet-shaped product is produced, collected and wound in a roll form, and subjected to subsequent processes.
In these preliminary steps (A, B, C), a predetermined test is carried out for each step by a testing person. For example, in the case of the step (A), during the transportation of the PVA source, the testing person confirms the defects (foreign substances, stains, twists, and the like) by eye inspection. Also, in the case of the step (B), in collecting and winding the obtained polarizing plate source in a roll form, the testing person confirms the defects (foreign substances, stains, knicks, twists, creases, and the like) by eye inspection at the timings of the start and the end of winding of the roll. Also, the polarizing plate source after bonding is automatically tested by a defect testing apparatus (a known apparatus for capturing images of foreign substances, stain, and the like with a camera, and determining the defects by image processing); the defects are confirmed by a monitor; and the test was mainly used for state management (supervision) by monitoring the defects.
Also, in the case of the step (C), in collecting and winding the obtained band-shaped sheet-shaped product source in a roll form, the testing person confirms the defects (foreign substances, stain, twist, surface-adhering substances, and the like) by eye inspection at the timings of the start and the end of winding of the roll, and performed the ranking (good, bad, permissibility of shipping) of the sheet-shaped product source by evaluating these defects.
Subsequently, as the posterior steps, there is (D) a step of testing the source roll. Here, the appearance of the sheet-shaped product roll is tested by a roll-form automatic source testing apparatus and/or by eye inspection of a testing person. The roll-form automatic source testing apparatus is a known apparatus that captures images of poor winding, poor appearance, and the like with a camera, and performs image processing to determine the defects. Also, there is (E) a step of cutting into a sheet-shaped product provided in separate sheets. Here, a sheet-shaped product is drawn out from the source roll, and is cut to have a predetermined size. As the cutting method, there are, for example, constant-measure cutting, continuous punching-out, and the like. Also, there is (F) a step of testing the sheet-shaped product provided in separate sheets. Herein, testing by a sheet-form automatic testing apparatus and by eye inspection of a testing person are carried out. The sheet-form automatic testing apparatus is an apparatus that automatically tests the defects of a sheet-shaped product provided in separate sheets, where light is radiated; images of the reflected light thereof or images of transmitted light thereof are captured with an imaging section such as a line sensor or a two-dimensional TV camera; and the defects are detected on the basis of the captured image data. Also, the image data are obtained in a state in which a polarizing filter for testing intervenes in the optical path between the light source and the imaging section. Typically, the polarization axis (for example, the polarization absorption axis) of this polarizing filter for testing is disposed to be in a state (crossed nicol form) perpendicular to the polarization axis (for example, the polarization absorption axis) of the polarizing plate that is an object of testing. By disposing it in crossed nicol, an image of total black is input from the imaging section if there are no defects; however, when there are defects, that part will not be black (and will be recognized as bright points). Therefore, the defects can be detected by setting a suitable threshold value.
As described above, in the posterior steps (D, E, F), the sheet-shaped product source wound in a roll form is drawn out and is cut into a sheet-shaped product provided in separate sheets of a predetermined size, followed by a predetermined defect testing to determine the quality for shipping.
As described above, in the previous steps, the testing of defects is carried out with a defect testing apparatus after forming the polarizing plate. In the steps, generally, a polarization filter for testing is disposed between the object of testing and the CCD camera, and bright points are detected by setting the polarization axis with the object of testing to be in a state of crossed nicol (0 degree cross). In detecting the bright points, the defects such as surface-adhering substances and internal foreign substances are detected as bright points. Also, in addition to this bright point detection, a method is adopted in which foreign substances are detected by capturing a transmitted light image of an object with a CCD camera and performing image analysis. Also, a method is adopted in which surface-adhering foreign substances are detected by capturing a reflected light image of an object with a CCD camera and performing image analysis.
Also, a sheet-shaped product testing system and a sheet-shaped product producing system described below are known (See Japanese Patent Application Laid-Open (JP-A) No. 2005-62165). The defects of a band-shaped polarizing plate source are detected; the position information of these defects is printed in a form of a bar code at the width-direction end part of the polarizing plate source; and the band-shaped polarizing plate source having the bar code recorded thereon is collected and wound in a roll form. Then, the band-shaped polarizing plate source is drawn out from the roll; the bar code printed at the width-direction end part of the polarizing plate source is detected; the site of the defects is marked on the basis of this bar code; and individual polarizing plates can be punched out from the polarization source after this marking. The punched and marked polarizing plates containing the defects are determined as bad products.
In the meantime, in accordance with the development of image capturing technique and image analyzing technique of recent years, the defects in μm units can be detected. Also, due to the demand for higher product quality and higher image quality of the displaying apparatus, there is a need for raising the precision of defect testing.
As described above, the steps of producing a sheet-shaped product are complex and made of numerous steps. In addition, the sheet-shaped product has a large width, has a large length, and is drawn out from the source in a roll form in each production step for performing the process of each step. Namely, the sheet-shaped product is drawn out in a band shape, and is collected and wound in a roll form again after the process is finished. During that period, the sheet surface is exposed to the outside, so that the sheet-shaped product is liable to be contaminated from the outside. In particular, there are cases in which the litters and dusts in the air may adhere to the surface, or the foreign substances in the processing liquid may adhere, followed by being dried as they are. However, these foreign substances adhering to the surface will not be the final defects by being forcibly removed in a later step (for example, removal by suction, removal by electrostatic adsorption, or the like, or by being subjected to a surface cleaning treatment or the like).
When the surface-adhering substances are determined as defects in this manner, the number of taking the sheet-shaped products will decrease, thereby raising a problem of lowering the yield. Also, in the case of producing a sheet-shaped product using the method of JP-A No. 2005-62165, the defects of the surface-adhering foreign substances are determined, as they are, as defects, are marked, and are treated as bad products after being punched out, thereby giving a cause of decrease in the yield.
In order to solve this, a method of determining whether the defects are surface-adhering foreign substances or not by image analyzing process or the like may be considered; however, this requires a complex algorithm and the data processing itself will be complex, hence not preferable.
The present invention has been made in view of the above, and an object thereof is to provide a test data processing apparatus and a test data processing method that determine the defects of surface-adhering foreign substances easily and perform data processing without treating the surface-adhering foreign substances as defects, by using a conventional testing method.
In order to solve the above-described problems of the prior art, the inventors of the present invention have made eager studies and, as a result, completed the following invention.